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vc: extract detecting control characters from do_con_write

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Move the control characters detection to a separate function dubbed
vc_is_control. It makes the 14 subexpressions a "bit" more readable. And
also simplifies next patches.

It moves also CTRL_ACTION and CTRL_ALWAYS to this new function, as they
are used exclusively here. While at it, these are converted to static
const variables.

And we use "& BIT()" instead of ">>" and "& 1".

Checked using symbolic execution (klee), that the old and new
behaviors are the same.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20200615074910.19267-18-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jiri Slaby 2020-06-15 09:48:50 +02:00 committed by Greg Kroah-Hartman
parent 917ae1a990
commit 754bda9807
1 changed files with 45 additions and 26 deletions
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71
drivers/tty/vt/vt.c
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@ -127,14 +127,6 @@ struct con_driver {
static struct con_driver registered_con_driver[MAX_NR_CON_DRIVER];
const struct consw *conswitchp;
/* A bitmap for codes <32. A bit of 1 indicates that the code
* corresponding to that bit number invokes some special action
* (such as cursor movement) and should not be displayed as a
* glyph unless the disp_ctrl mode is explicitly enabled.
*/
#define CTRL_ACTION 0x0d00ff81
#define CTRL_ALWAYS 0x0800f501 /* Cannot be overridden by disp_ctrl */
/*
* Here is the default bell parameters: 750HZ, 1/8th of a second
*/
@ -2691,13 +2683,56 @@ static inline unsigned char vc_invert_attr(const struct vc_data *vc)
((vc->vc_attr & 0x07) << 4);
}
static bool vc_is_control(struct vc_data *vc, int tc, int c)
{
/*
* A bitmap for codes <32. A bit of 1 indicates that the code
* corresponding to that bit number invokes some special action (such
* as cursor movement) and should not be displayed as a glyph unless
* the disp_ctrl mode is explicitly enabled.
*/
static const u32 CTRL_ACTION = 0x0d00ff81;
/* Cannot be overridden by disp_ctrl */
static const u32 CTRL_ALWAYS = 0x0800f501;
if (vc->vc_state != ESnormal)
return true;
if (!tc)
return true;
/*
* If the original code was a control character we only allow a glyph
* to be displayed if the code is not normally used (such as for cursor
* movement) or if the disp_ctrl mode has been explicitly enabled.
* Certain characters (as given by the CTRL_ALWAYS bitmap) are always
* displayed as control characters, as the console would be pretty
* useless without them; to display an arbitrary font position use the
* direct-to-font zone in UTF-8 mode.
*/
if (c < 32) {
if (vc->vc_disp_ctrl)
return CTRL_ALWAYS & BIT(c);
else
return vc->vc_utf || (CTRL_ACTION & BIT(c));
}
if (c == 127 && !vc->vc_disp_ctrl)
return true;
if (c == 128 + 27)
return true;
return false;
}
/* acquires console_lock */
static int do_con_write(struct tty_struct *tty, const unsigned char *buf, int count)
{
struct vc_draw_region draw = {
.x = -1,
};
int c, next_c, tc, ok, n = 0;
int c, next_c, tc, n = 0;
unsigned int currcons;
struct vc_data *vc;
unsigned char vc_attr;
@ -2755,23 +2790,7 @@ rescan_last_byte:
&param) == NOTIFY_STOP)
continue;
/* If the original code was a control character we
* only allow a glyph to be displayed if the code is
* not normally used (such as for cursor movement) or
* if the disp_ctrl mode has been explicitly enabled.
* Certain characters (as given by the CTRL_ALWAYS
* bitmap) are always displayed as control characters,
* as the console would be pretty useless without
* them; to display an arbitrary font position use the
* direct-to-font zone in UTF-8 mode.
*/
ok = tc && (c >= 32 ||
!(vc->vc_disp_ctrl ? (CTRL_ALWAYS >> c) & 1 :
vc->vc_utf || ((CTRL_ACTION >> c) & 1)))
&& (c != 127 || vc->vc_disp_ctrl)
&& (c != 128+27);
if (vc->vc_state == ESnormal && ok) {
if (!vc_is_control(vc, tc, c)) {
if (vc->vc_utf && !vc->vc_disp_ctrl) {
if (is_double_width(c))
width = 2;